Just wondering if reduction rings will incease the light intensity that hits the reduced area? I guess theoretically it should, but reduction rings weren't a thing way back when I was last doing underwater photography - but I guess we could have bodgered up something from some plumbing fittings if we had thought to.

I’m no scientist but general observation leads me to think, no they don’t. I use reduction rings with Retra strobes and can’t recall ever thinking I need to turn them down.

My own experience, when using a snoot which is not dissimilar, is that more light is needed because of the way the light is blocked by the constrictions of the funnel. The same could be true even of reduction rings.

But like I say, I’m no scientist and perhaps my subjective view is wrong 😜